Module drivers core

Module drivers/core

Maintainers

	Slack	Github
Stefan	@stefandebruyn	@stefandebruyn
Tianshu	@thetianshuhuang	@thetianshuhuang

Related Issues

• Abstract threaded robot type

Usage

robot module

Contains the lowest-level robot class.

• RobotFrame - A threaded encapsulation of subsystem states and an instruction sequence associated with them. Implementations should override loop

robotcore module

core.robotcore contains abstract representations of robot subsystems intended to provide a common interface for both simulated and actual robots.

• Subsystem - Parent of all subsystems. Holds a unique name by which to identify the system
• Motor - Parent of all motor types. Holds a robotmotion.MotionState and the timestamp of the last update
• StepperMotor - Type of Motor that can be updated with a position x and a timestamp t. Velocity, acceleration, and jerk are then calculated by approximating the slopes of dx/dt, d2x/dt2, and d3x/dt3.
• BinaryActuator - An actuator with a binary state, such as a servo claw
• AnalogActuator - An actuator with a bounded state, such as a linear slide

robotmotion module

core.robotmotion contains things relating to motion planning and profiling. Like robotcore, this module is built to be common ground for the simulator and the robot.

• MotionProfile - Represents a motion profile fitted to some MotionConstraints and a pair of MotionStates. Target states at specific points in time within the profile can be fetched with state_at(float)
• MotionConstraints - The maximum velocity, acceleration, and jerk magnitudes allowed for a particular profile
• MotionState - An instantaneous kinematic state in 1D space; <pos, vel, accel, jerk, time>

profiling module

Contains the actual motion profile generation algorithms.

• make_trap - Generates a trapezoidal (three-segment, acceleration-limited) profile
• make_scurve - Generates an S-curve (seven-segment, jerk-limited) profile

The profiling algorithms have some drawbacks. See the notes at the top of drivers/core/profiling.py.

An overly verbose example of using a motion profile:

from core.robotmotion import MotionState, MotionConstraints
from core.profiling import make_scurve

initial_position = 0
initial_velocity = 0

final_position = 100
final_velocity = 0

max_velocity = 10
max_acceleration = 5
max_jerk = 5

profile = make_scurve(MotionState(initial_position, initial_velocity),
                      MotionState(final_position, final_velocity),
                      MotionConstraints(max_velocity, max_acceleration, max_jerk))

middle_state = profile.state_at(profile.duration / 2)

with middle_state as s:
    middle_pos, middle_vel, middle_accel, middle_jerk = s.x, s.v, s.a, s.j